Colossal dielectric properties of Li- and Sm- based perovskite ceramics: A combination of first-principles calculations and experiments

Abstract

The Li1/2Sm1/2Cu3Ti4O12 ceramic, which is in the ACu3Ti4O12 class, was investigated by means of both experimental and theoretical approaches. In our experiments, it was made via a solid-state reaction. Our XRD measurements revealed that the crystal structure of this sintered ceramic possesses a body-centered cubic system with an Im3 space group. Moreover, CuO and Sm4Ti3O12 impurity phases were observed. At 1 kHz and 20 °C, a high dielectric constant of approximately 3615–3838 and a rather low loss tangent of 0.119–0.185 were achieved for Li1/2Sm1/2Cu3Ti4O12 ceramics. According to our density functional theory calculations, we found that Li and Sm ions preferably occupy Cu and Ca sites, respectively. From our electron density analysis, there is a charge transfer from Li to Sm in this ceramic, although the valence states of Cu and Ti are constant. Cu+ and Ti3+ ions were detected by incorporating an oxygen vacancy into this structure. Based on our results, an internal barrier layer capacitor is a significant contributor to the enormous dielectric characteristics of this ceramic.